Hello all, was wondering if, as the title says, there are octal equivalents.
The tubes will be triode strapped in a single ended design.
My knowledge is very minimal to non existent in this area.
Thanks in advance for any advice.
Cheers, Crazy Bill
The tubes will be triode strapped in a single ended design.
My knowledge is very minimal to non existent in this area.
Thanks in advance for any advice.
Cheers, Crazy Bill
The 6DZ7 contains two power pentodes which are almost identical to the EL84 (some of the limiting values of the 6DZ7 are higher than that of the EL84). But the two pentodes share the connections to the cathodes and to the screen grids. Because of the shared connection to the screen grids, you can't run the two pentodes seperate as triodes, but you can run the two pentodes parallel in triode mode (so you would need 2 x 6DZ7 to make a stereo triode SE amplifier).
B.t.w.: The SV83 is not equivalent to the EL84.
B.t.w.: The SV83 is not equivalent to the EL84.
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Talking about looks: You should change "found" in your motto/signature to "find".
There is a possible 'found' interpretation, if you are setting up (founding) new Flat Earth Believing groups ;-)
The interesting thing about English is that that interpretation completely reverses the meaning of the other one, if 'find' was intended.
The interesting thing about English is that that interpretation completely reverses the meaning of the other one, if 'find' was intended.
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No there is none. If you want an octal socket, them mount EL84 in a octal adapter.
Not sure if your post was in jest, or not.
I asked “why“ because OP will receive more useful suggestions if we know what he wants to do with his “octal EL84s”.
If your tube will be triode strapped why not consider one of the
TV vertical sweep triodes of which there are several to choose from
like 6CK4?
TV vertical sweep triodes of which there are several to choose from
like 6CK4?
Yes, you are right.
But it's a metal tube so, why not put a radiator around it ? 😀
1. Designing from scratch is one thing. You can design according to the calculations the the tube requires.
Use a 6CK4, a 6V6 Triode wired, an EL84 and design the amp to work.
2. Building to a fixed parts list, and with a fixed schematic, including a minimally specified power transformer, is another thing.
Just for starters . . .
EL84 filament is 0.76 Amps; Triode wired u is less than 19; plate resistance is about 1700 Ohms; 7 to 10V bias.
6V6 filament is 0.45 to 0.5 Amps; Triode wired u is about 9; plate resistance is about 2000 Ohms; perhaps 10 to 14V bias.
6CK4 filament is 1.25 Amps; Is a Triode, u is 6.6; plate resistance is 1200 Ohms; perhaps 28V bias.
Optimum output transformer primary impedance, B+ voltage, filament currents, required peak driver voltage swing, driver stage gain, etc. will be different for all these 3 tubes.
Decide on an output tube, and design according to its needs.
Use a 6CK4, a 6V6 Triode wired, an EL84 and design the amp to work.
2. Building to a fixed parts list, and with a fixed schematic, including a minimally specified power transformer, is another thing.
Just for starters . . .
EL84 filament is 0.76 Amps; Triode wired u is less than 19; plate resistance is about 1700 Ohms; 7 to 10V bias.
6V6 filament is 0.45 to 0.5 Amps; Triode wired u is about 9; plate resistance is about 2000 Ohms; perhaps 10 to 14V bias.
6CK4 filament is 1.25 Amps; Is a Triode, u is 6.6; plate resistance is 1200 Ohms; perhaps 28V bias.
Optimum output transformer primary impedance, B+ voltage, filament currents, required peak driver voltage swing, driver stage gain, etc. will be different for all these 3 tubes.
Decide on an output tube, and design according to its needs.
If you are making a single ended amplifier use a proper output tube like 2a3 ( 4 pin but fits an octal cutout) or 6B4G (octal). 2a3 can work with 2.5v AC filaments, 6B4G uses 6.3v which is best DC with a voltage reg by Rod Coleman (Lyrima). Separate filament supplies to each tube.
If you want to triode strap a pentode and get the same gain as EL84 in triode you should use a 7591. There's a new version by JJ Tesla at a good price. Czech Republic so freely available.
If you want to triode strap a pentode and get the same gain as EL84 in triode you should use a 7591. There's a new version by JJ Tesla at a good price. Czech Republic so freely available.
andyjevans,
Good point about the JJ 7591S!
Simple, because the driver and the output tubes can all use a common AC filament secondary;
Sounds good!
And the 7591S is a lot less expensive than a 2A3 or 6B4G.
But you will get less power than a 2A3 or 6B4G (just like a triode wired EL84 that has less power too).
Also, the output transformer needs a higher impedance primary than a 2A3/6B4G.
7591S filament is only 0.8 Amps; Triode wired: u is about 16; plate resistance is about 1700 Ohms; about 10V bias.
. . . Or try another quiescent operating point.
I am currently using JJ 7591S in a push pull amplifier (not single ended as in the original poster requested. It is in a thread that I started on the Tubes / Valves (diyAudio).
I recently changed the B+ filter from choke input, to 2 uF capacitor input filter, and almost doubled the output power, at even lower 2nd and 3rd harmonic distortion (compared at 1 Watt).
I use the amplifier for near field listening, so 1 Watt is all I need, even though the output power is several times that.
Eurotubes.com ships new (and vigorously re-tested) 7591S to many countries besides the US.
I am blessed, I just drive over to Eurotubes and pick mine up.
Good point about the JJ 7591S!
Simple, because the driver and the output tubes can all use a common AC filament secondary;
Sounds good!
And the 7591S is a lot less expensive than a 2A3 or 6B4G.
But you will get less power than a 2A3 or 6B4G (just like a triode wired EL84 that has less power too).
Also, the output transformer needs a higher impedance primary than a 2A3/6B4G.
7591S filament is only 0.8 Amps; Triode wired: u is about 16; plate resistance is about 1700 Ohms; about 10V bias.
. . . Or try another quiescent operating point.
I am currently using JJ 7591S in a push pull amplifier (not single ended as in the original poster requested. It is in a thread that I started on the Tubes / Valves (diyAudio).
I recently changed the B+ filter from choke input, to 2 uF capacitor input filter, and almost doubled the output power, at even lower 2nd and 3rd harmonic distortion (compared at 1 Watt).
I use the amplifier for near field listening, so 1 Watt is all I need, even though the output power is several times that.
Eurotubes.com ships new (and vigorously re-tested) 7591S to many countries besides the US.
I am blessed, I just drive over to Eurotubes and pick mine up.
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